This invention relates to a computerised tracing apparatus used to trace the perimeter of eyeglass frames and lenses to determine the shape of the lenses or frames.
Eyeglass frames are produced in a wide variety of shapes depending on the design of the frames. The corresponding eyeglass or ophthalmic lenses that will be mounted in the eyeglass frames must be shaped to have a conforming perimeter corresponding to the frame into which they will be mounted.
Generally, ophthalmic lenses are produced with various optical correction factors and have a uniform perimeter shape when produced and are termed lens blanks. A person will select the eyeglass frame most pleasing to him or her and, typically, it is the function of an optical dispensary to shape the lenses blanks to conform or fit into the particular selected eyeglass frame. Once the lens blanks have been shaped, they are mounted in the eyeglass frame and ready to wear.
In the past, the lens grinders which are used to grind the lens blanks include those that are controlled by mechanical patterns which produce perimeter shapes on the lens blanks that correspond to the eyeglass frames into which the shaped lens blanks produced from the lens blanks are to be mounted. An inventory of these mechanical patterns is used to control the grinding process to shape the lens blanks to the desired perimeter shapes.
More recently, computer controlled grinders have been employed to grind a lens blank periphery into the desired shape, as shown for example, in my corresponding U.S. Pat. No. 5,683,288. For computer controlled grinders, it is preferable to have digital encoders to trace the perimeter shape of an eyeglass frame or lens to enable further lens blanks to be shaped to a corresponding perimeter shape quickly and expediently. Such digital encoders can be referred to as patternless tracers and a number of devices to trace or digitally encode the perimeter shape of an eyeglass lens or frame have been proposed. The patternless tracers trace the periphery of a lens or eyeglass frame to produce a data set representative of the shape of the lens or frame which has been traced. An example of a digital encoder or patternless tracer of this type is found in U.S. Pat. No. 5,333,412 to Matsuyama for apparatus and method of obtaining processing information for fitting lenses in eyeglass frames and an eyeglass grinding machine. Another computerised edge tracing system is disclosed in U.S. Pat. No. 4,912,880 to Haddock et al.
Due to the varying types of designs of eyeglass frames, including both the shape of the lens mounting portion of the frames as well as the variety of materials from which the frames are constructed, it is desirable to have a frame tracer which can trace a wide variety of shapes of lenses to accommodate the wide variety of eyeglass frame materials of the products that are available in the marketplace. Moreover, it is desirable to have a lens tracer system which allows the eyeglass frames to be mounted in a simple structure which requires a minimum of operator set-up before the eyeglass frames, lenses or patterns which are to be traced can be traced by the tracing machine.
In this regard, it is desirable to have a frame lens tracer system in which the frame or lens to be traced can be mounted without manipulation or adjustment of numerous clamps or settings or other mechanical devices to xe2x80x9ccenterxe2x80x9d the frame or lens in the holding mechanism of the tracer. Moreover, it is desirable to have a tracer which can be used to trace a wide variety of materials such as wire frames and plastic frames. Preferably, the tracers should be capable of tracing any arbitrary eyeglass frame or lens peripheral shape including edges that provide varying radii of curvature from a very large radius of curvature of a smooth arc to a very small radius of curvature of a sharp arc or cusp. It is preferable that the tracer apparatus not deflect or deform the frames during tracing, which can result in errors in the tracing readings produced by the tracer. Moreover, the tracer apparatus should not bind on or come free of the edge which is being traced as these conditions result in errors in the tracing readings produced by the tracer.
In one of its aspects, the invention provides apparatus to trace the perimeter shape of an eyeglass frame or lens comprising a base including holding means and a stylus. The apparatus includes rotation means operable to rotate said stylus relative to said base and rotation encoder means to provide signalling representative of relative rotation between said stylus and said base, and horizontal movement means operable to move said stylus horizontally relative to said base including horizontal movement encoder means to provide signalling representative of relative horizontal displacement between said stylus and said base. The apparatus has vertical movement means operable to move said stylus vertically relative to said base and vertical movement encoder means to provide signalling representative of relative vertical displacement between said stylus and said base. Whereby the stylus can trace the perimeter of an eyeglass frame or lens held by said holding means.
In another of its aspects, the invention provides an apparatus to trace the perimeter shape of an eyeglass object, namely a frame or a lens, comprising a base and means to hold an eyeglass object to the base. The apparatus further includes a stylus to contact the eyeglass object and actuator means operable to displace the stylus with respect to the base in three directions, namely rotationally about a pivot point, horizontally and vertically. The apparatus also includes encoder means to produce signalling representative of the rotational, horizontal and vertical displacement of said stylus with respect to the base and control means to activate the actuator means to control the rotational, horizontal and vertical displacement of the stylus whereby the stylus is displaced to trace the perimeter of the eyeglass object and the position of the stylus during said trace is signalled by the encoder means.
In yet another embodiment, the invention includes a method of tracing the perimeter shape of an eyeglass frame or lens comprising the steps of releasably securing an eyeglass object, namely a frame or lens, to a base and biasing a stylus into contact with said eyeglass object. The method provides for rotating the stylus substantially one revolution about a pivot point with respect to the base and encoding the vertical, horizontal and rotational displacement of the stylus at discreet intervals during the revolution.
And in yet another embodiment, the invention provides a method for seating alignment of apparatus to trace the perimeter shape of an eyeglass frame that includes a base, means to hold an eyeglass frame to the base, a stylus having a pointed projection to contact the eyeglass frame, actuator means operable to displace the stylus with respect to said base in at least two directions, namely, horizontally and vertically, comprising attempting seating alignment until seating of the pointed projection of the stylus in a lens seating groove of an eyeglass frame occurs or a predetermined number of attempts were not successful, each attempt including the steps of homing the stylus to a start position at a selected vertical displacement location and horizontal displacement location. The method further includes moving the stylus horizontally outwardly to an end position and adjusting the vertical displacement location of the start position of the stylus by determining the change in vertical displacement of the stylus at the end position and, for an increase in vertical displacement of the stylus, decreasing the vertical displacement location of the start position of the stylus; but for no increase in vertical displacement of the stylus, increasing the vertical displacement location of the start position of the stylus.
The preferred embodiments of the invention will now be described with reference to the attached drawings which are briefly described as follows.